The present invention relates to a flexible polymeric sponge material, and more particularly, to a sponge rubber rug underlay compound having improved load bearing capacity.
Rub underlay is frequently made from a filled rubber, either natural or synthetic. The one most commonly used is styrene-butadiene rubber (SBR). SBR provides a durable, resilient, and flexible rug underlay when combined properly with various fillers, antioxidants, cure accelerators, and other compounding ingredients. Therefore, while the present invention may be used advantageously in any rubber rug underlay, it is especially useful with an SBR, and will be described in connection therewith. Conventionally, the filler material has been soft clay plus calcium carbonate, although it is also known to use calcium carbonate alone. A typical calcium carbonate is the one known commercially as Whiting. Other fillers which are used include alumina tri hydrate.
Among the properties for which any particular rug underlay composition is tested is its load bearing capacity; i.e., the amount by which the rug underlay will be compressed under a given load, or conversely, the force the underlay will exert, or the load it will support, when compressed by a given percentage. It should be readily apparent that for a composition which is to be used for rug underlay, the load bearing capacity is an especially important property of the composition.